Broadly defined, the research area of this project is a study of the mechanisms of DNA repair in eukaryotic cells, particularly human lymphocytes. This topic addresses not only basic cell processes, but also has implications for cancer induction and treatment. Specifically, the study is designed to measure the effects of inhibition of topoisomerase II, alpha DNA polymerase, and beta DNA polymerase upon repair of DNA damaged by different types of chemical agents. The study is designed to use human lymphocyte cultures because they provide synchronous cell populations and easily-monitored end point measurements of sister chromatid exchanges and chromosomal aberrations. Preliminary work with lymphocyte cultures indicated that this approach is both feasible and informative. The results showed that inhibition of topoisomerase II by novobicin interfered with the ability of the cell to repair DNA damage caused by a polyfunctional alkylating agent (TEM), but did not significantly hinder repair of damage caused by a monofunction alkylating agent (EMS). These results agree with the current proposed model of action of topoisomerase II in forming double strand breaks and then rejoining the strands after repair has been effected. Further investigation along these same lines with intercalating alkylating agents (such as Mitomycin C which has potent antitumor activity) should provide further insight into the role of topoisomerase II and its role in DNA repair. Additional experiments with agents known to cause single strand breaks (such as bleomycin) would be useful for comparison, as would experiments which utilize inhibitors of alpha and Beta DNA polymerases. It would be interesting to see if alpha and Beta DNA polymerases are equally involved in the repair of different types of DNA damage.